Role of Microstructure in Promoting Fracture and Fatigue Resistance in Mo-Si-B Alloys
- ORNL
An investigation of how microstructural features affect the fracture and fatigue properties of a promising class of high temperature Mo-Si-B based alloys is presented. Fracture toughness and fatigue-crack growth properties are measured at 25 and 1300 C for five Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} containing alloys produced by powder metallurgy with {alpha}-Mo matrices. Results are compared with previous studies on intermetallic-matrix microstructures in alloys with similar compositions. It is found that increasing the {alpha}-Mo phase volume fraction (17-49%) or ductility (by increasing the temperature) benefits the fracture resistance; in addition, {alpha}-Mo matrix materials show significant improvements over intermetallic-matrix alloys. Fatigue thresholds were also increased with increasing {alpha}-Mo phase content, until a transition to more ductile fatigue behavior occurred with large amounts of {alpha}-Mo phase (49%) and ductility (i.e., at 1300 C). The beneficial role of such microstructural variables are attributed to the promotion of the observed toughening mechanisms of crack trapping and bridging by the relatively ductile {alpha}-Mo phase.
- Research Organization:
- Oak Ridge National Laboratory (ORNL)
- Sponsoring Organization:
- FE USDOE - Office of Fossil Energy (FE); SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 989540
- Country of Publication:
- United States
- Language:
- English
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